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MG Midget and Sprite Technical - HS2 vacuum advance-float level

I'm getting ready to try out the original HS2s on my '63 in place of the Weber. I'm wondering where you'd hook up the vacuum advance line from the distributor. Maybe it will be obvious when I finally get home to look at some manuals....maybe not.
I'm also annoying folks on another forum asking about float level. 1/8" clearance but where exactly? Here's what I've done, I have grose jets in there, I've set it such that the float is at 1/8" of clearance, from the bottom of the float's bracket to the plane of the edge of the cover when the jet shuts down. See picture. Some say 1/8" at the front edge of the float. Anyone ever come across an actual measurement so I can simply run it til it shuts off and physically check the level? I understand it's pretty critical, or am I being too anal?
Maybe the measurement will end up the same, given the float top is angled a bit.


J Van Dyke

J -

Being a Zenith guy, I can't comment on your SU. But what I can suggest is that you ditch the Grose Jets and go back to the needle-type float valves. I had all kinds of trouble with a Grose Jet in my ZS carb several years ago, including failure to seal, bad flooding, being immobilized miles from home, lots of fuel in my oil, a charcoal canister filled with gasoline, and a ruined catalytic converter. And it's not just me - I've read similar reports in this very BBS, and in addition I spoke with a guy a while back who was experiencing carb overflow in his TR6, and - you guessed it - he'd had it fitted with Grose Jets. They look way cool in the catalogs, and the blurb would have you believe they're worth their weight in gold. But they've been known to cause problems.

Just so you know,

-:G:-
Gryf Ketcherside

Yeah, I know about the jaded past of the Grose jets, but there's also lots of guys who've run them for years with great success. I figured they're in there, I'll try them out. I'm trying to test the SUs with lots of tinkering but looking to avoid throwing parts at it unless I have to. I think I found the port for the vac advance, tiny little barbed fitting pointing forward on the intake, just inboard of the forward carb.
Float level: I've concluded I'm splitting hairs and I've got to darn close to perfect.

I'll be observant for signs of flooding or starving and if anything seems weird I'll get a set of viton tipped jets and seats....if the carbs seem worth it.
J Van Dyke

Jeff,
Yes, that is the vacuum advance tap. This is ported vacuum. Hard to tell if you still have the original vacuum advance module on the distributor which would expect ported vacuum. I do not know what vacum signal your Weber was sending, either. It is possible that the PO who installed the Weber modified the distributor for manifold vacuum.
David "just removed the Grose-Jets from my Bugeye" Lieb
David Lieb

Thanks, first I've heard of the ported vac vs. manifold vac issue. I doubt the dist. was changed so it was seeing more vacuum then it should, meaning a bit too advanced under high vac situations, or all? I set timing with it disabled....oh well, runs good on the Weber with the dizzy hooked to the Weber's port. Makes me wish I had a timing light with an advance on it. Maybe I'll just tap the intake on the balance bar just in case I need manifold vacuum for something, the dist. or crankcase venting. There's three bosses on it, I assume the two on the ends (currently with threaded holes) are supposed to hold the water pipe? there's a third unthreaded I thought I'd drill out and tap and cap.
J Van Dyke

Here is a coulple of pics of my HS2s for a 71 midget,

your looking for a small "charlie brown" christmas tree thing on the side of the front carb...its really small, but hopefully the pics can giuld you in the right direction

Prop


Prop

and a 2nd shot...Btw your looking at the tip of the green ink pen.

Prop





Prop

Yep, thanks that's the guy. Now I wonder about ported vac vs. normal manifold vac and effects on advance. I'd guess either a regular dist, with manifold vacuum on it would either always be "on" or come in quicker/longer?
In any event, I'll check my timing closely when I put the SUs on and see what happens.
J Van Dyke

J Van,

I think we are on a simialr plan, Im planing to evac thur the intake manifold instead of the carbs, simply for the sake of keeping the carbs cleaner,,,other wise all that oil mist will get sucked down the carbs, and you know where that leads.

Prop


Prop
Prop

Just got back from the garage, got the SUs on but not fired up, kinda late now. Man it's a pain getting the two center manifold retaining nuts on there with the carbs and heat shield in place! I don't think I need shims with the stock intake and Pacesetter header (I had some with the Weber's Pierce intake). Yeah, forgot to tap the stupid balance pipe, oh well, I'm 90% sure it's coming back off pretty quick anyway.
J Van Dyke

Maybe it won't come off too soon.
Bolted on the HS2s. Fired right up and ran really well, cold, no adjustments at all yet but good feeling to have the original 46 year old car, with it's original 46 year old engine now powered by it's original 46 year old carbs. I think I saw her smile. I blipped the throttle a couple times just to see the pistons rise and fall. Too cool.
Interestingly it sounds much much better. I always had a funny rattling sound that I chose to ignore as I was worried it was deep in the bowels of the motor. That noise is gone. Not that that means much but I'm pretty encouraged so far.
Let the tuning begin!
BTW I love the cable operated starter, can simply reach over and pull the cable to engage the starter which allows me to use one hand to hold the choke/throttle where I want it while cranking.
J Van Dyke

Jeff,
The vacuum advance module on the distributor will have a part number on it. You should be able to cross-reference that number to determine what year of car it is from. This will tell you whether it wants manifold vacuum or ported vacuum.
David "air head" Lieb
David Lieb

Update. Did first tuning session, by the book, several actually, all essentially the same. During warm up I noticed it was running almost entirely off the rear carb (by blocking intake with hand could feel big difference in air suckage).
Got flow equalized via throttle screws, linkage loose, used a hose to the ear (seems pretty imprecise, should get or mock up a uni-sync). On to mixture check, started both at 12 flats down, piston lift test on front carb got an increase in rpm but after moving jet adjusting nut up to lean out it had no discernible effect. Piston test on rear carb did nothing. Moved both nuts around seeking for some change but got nothing, returned both nuts to 12 and decided to proceed. Setting choke linkage had the front set noticeable "offline" with the rear but both jets start to drop at the same time so that was the goal I figured and both return up all the way when cable is slackened. My choke cable (set up for Weber) is a bit short, therefore tight and doesn't operate all that great, might have to redo the whole thing. I'm going to put on the air cleaners and housing and road test it (hopefully tonight if SWMBO doesn't give me stink eye). BTW I ended up putting four springs on as there seemed to be a tad of slop in the linkage so I have one spring to each side of the throttles, not the center and one spring each on the choke linkage. So far it's easily reversible back to the Weber except I might have ruined the choke cable by now.
Also wonder why this source says FRONT carb like that?? First. Bother me a bit that I don't get any reaction raising the rear carb's piston, maybe I still have unequal and it's running mostly off the front?



J Van Dyke

You should start off with both carbs having ~same mixture setup. Then set idle so that both carbs are drawing same amount of air. Use the throttle stops for this.

Then, pull on throttle cable and watch the spindles carefully. The cable should take up the slack and open the throttle spindles at exactly the same time; if not, you should slacken screws on one side, adjust, tighten and repeat cable pull. There is a little trial and error here.

When carbs have same air input on idle, and both open at same time on throttle cable pull, you can focus on the mixture.

This is not as hard as it sounds; and once adjusted and tightened, everything should stay put for long periods (at least for me, anyway!).


HTH

A
Anthony Cutler

okay, thanks, maybe I moved off the "air synch" step too quickly I'll double check that.
BTW what's a good idle speed to work with? I like low idles but HATE stalls so I'm thinking 900ish.
Think I should get a uni=sync?
J Van Dyke

J Van Dyke,

the little tube that runs from the fuel bowl to the jet, is notorious for collecting dirt, varnish and debries due to poor/dirty filters and in genral just over time,

disconnect the tube from the jet end and use carb cleaner with the tiny straw and work it thur the tube

When I 1st. got my midget, I had a horrable time trying to get the rear carb to work, much like your experiancing and an old mechanic showed me what was the problem, once the tube was cleaned out, it ran like a charm,,,,btw add 2 filters back to back to prevent this, a big one and a small one, small closer to the carb

Prop
Prop

I think I had that all apart earlier this winter. I know the rear carb is feeding fuel as it was running mostly on that carb when I first fired it up. I'm guessing my untrained ear isn't picking up the difference in the noise from the tube (the hiss) from carb to carb, so I'm running mostly off the front now, which is why the piston lift with that carb has an effect but not on the rear carb, it's theory anyway. You'd think mixture nut would effect running especially on the front carb, but it doesn't, I never went more than 6 flats either way from the 12 down starting point though.
J Van Dyke

Took a few little runs, to bring kids away to friends. On the way home, the throttle cable pulled loose....oops. That was embarrassing. Good thing it's little, right in the middle of an intersection I had to jump out and push it over.
Quick cobbled it back together and got home. I don't like the look of that linkage, seems like a bunch of slop in it.
It definitely doesn't pull as hard but not very fair to compare with one complete rookie's first attempt at tuning. They run "smoother" than the Weber, don't hesitate the Weber can. I swear they're quieter then the Weber, less "induction noise"?
If I can get a bit better performance I'll be happy. I'll be even happier if mpg goes up a bit.
I'll go back over the whole adjustment procedure and keep tinkering. It's fun.
J Van Dyke

This thread was discussed between 27/05/2009 and 30/05/2009

MG Midget and Sprite Technical index

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